Patient-specific bone grafting system and method

ABSTRACT

A system for generating a model of a patient specific cut guide instrument for harvesting a graft comprises a model of a graft defined by an implant interface surface, a bone interface surface, and a spatial geometry therebetween, the model being specific to a patient. A patient-specific instrument generator outputs the model of the patient specific cut guide instrument, the patient-specific instrument generator including a position determination module for orienting and positioning at least a first guide axis, and for positioning an abutment on a model of a donor bone as a function of the spatial geometry, and an instrument body generator module for generating a model of the patient specific cut guide instrument comprising a body supporting a cut guide to perform a depth cut in the donor bone positioned and oriented as a function of a contact of the body with the abutment on the donor bone, and of the model of the graft, a first guide channel for alignment with the first guide axis, and at least one anchor guide for securing the patient specific instrument cut guide on the donor bone as abutted with the abutment and aligned with the first guide axis, whereby the patient specific cut guide instrument is used for harvesting the graft for subsequent implanting without alterations to the spatial geometry of the graft.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims the priority of U.S. Provisional PatentApplication No. 62/167,686, filed on May 28, 2015, and incorporatedherein by reference.

TECHNICAL FIELD

The present application relates to orthopedic shoulder surgery and moreparticularly to patient-specific instrumentation used to harvest bonegrant and implant same. For example, the system and method may beapplied to reverse shoulder arthroplasty, featuring humeral bone graftfor eroded glenoids.

BACKGROUND OF THE ART

Bone grafts are occasionally used in orthopedic surgery. Bone grafts areused to fill gaps between a recipient bone and an implant. Boneautografts have the ability to be osteoinductive, osteogenic, and/orosteoconductive and therefore are an advantageous choice for orthopedicsurgery, to interface off-the-shelf implants to bone. Allografts arealso commonly used.

For example, in reverse shoulder arthroplasty, the shoulder jointinvolves implants that replicate the native shoulder joint, but in areverse arrangement with the scapula forming the joint head, and thehumerus forming the socket. Reverse shoulder arthroplasty is often usedbecause of glenoid deformities and/or rotators cuff malfunction.Considering that the humerus must be machined and converted into asocket, there is a source of graft that can be used to correct glenoiddeformities, and/or to create an interface between an implant and theglenoid. Humerus bone grafts may be harvested to compensate the boneloss due to glenoid erosion. As subchondral bone has been shown to beeffective in stabilizing glenoid implants more than cancellous bone, itis desirable to harvest grafts in the humerus.

However, grafting techniques involving for example autografts commonlyinvolve some graft adaptation steps, e.g., machining, alterations, forthe graft to have a desired geometry for subsequent implantation.However, such machining steps may add time to a surgical procedure.

SUMMARY

It is an aim of the present disclosure to provide a method forharvesting a graft that addresses issues related to the prior art.

It is a further aim of the present disclosure that the method forharvesting a graft be used to harvest humeral bone grafts for reverseshoulder arthroplasty.

It is a still further aim of the present disclosure to providepatient-specific instruments for harvesting bone grafts for subsequentimplantation.

It is a still further aim of the present disclosure that thepatient-specific instruments be used in reverse shoulder arthroplasty.

Therefore, in accordance with a first embodiment of the presentdisclosure, there is provided a method for harvesting a graft having atleast an implant interface surface, a bone interface surface, and aplanned spatial geometry therebetween, the method comprising: obtaininga cut guide instrument specific to a patient's anatomy; resurfacing anexposed surface of a donor bone to form one of an implant interfacesurface and a bone interface surface of the graft; securing the cutguide instrument to the bone relative to resurfaced exposed surface;performing a depth cut in the donor bone to form the other of theimplant interface surface and the bone interface surface of the graftwith the planned spatial geometry; and harvesting the graft from thedonor bone.

Further in accordance with the first embodiment, resurfacing the exposedsurface of the donor bone in some instances comprises resurfacing theexposed surface to form a planar surface used as the implant interfacesurface.

Still further in accordance with the first embodiment, performing thedepth cut in some instances comprises forming the bone interface surfaceinto another planar surface, the exposed surface being non parallel tothe bone interface surface.

Still further in accordance with the first embodiment, harvesting thegraft in some instances comprises forming a cylindrical body between theimplant interface surface and the bone interface surface, an axis of thecylindrical body being normal to the implant interface surface.

Still further in accordance with the first embodiment, harvesting thebone in some instances comprises securing an implant against the implantinterface surface and removing the implant and graft from the donorbone.

Still further in accordance with the first embodiment, harvesting thegraft in some instances comprises harvesting the graft to obtain thespatial geometry based on one of the Walch glenoid indication and Favardglenoid indication in a reverse shoulder arthroplasty.

Still further in accordance with the first embodiment, harvesting thegraft in some instances comprises harvesting the graft from a humerusbeing the donor bone, and further comprising implanting the graft and animplant onto the glenoid in reverse shoulder arthroplasty.

Still further in accordance with the first embodiment, the graft in someinstances is implanted onto a recipient bone without further alterationsto the graft after said harvesting from the donor bone.

Still further in accordance with the first embodiment, resurfacing theexposed surface in some instances comprises installing a guide rod andmoving a resurfacing tool on the guide rod.

Still further in accordance with the first embodiment, securing the cutguide instrument on the bone in some instances comprises sliding the cutguide instrument along the guide rod and into abutment with the exposedsurface.

Still further in accordance with the first embodiment, a peg bore insome instances is formed in the graft, the peg bore being coaxial with ahole in the donor bone made by insertion of the guide rod.

Still further in accordance with the first embodiment, forming the pegbore in some instances is removing the guide rod.

Still further in accordance with the first embodiment, resurfacing theexposed surface of the donor bone in some instances comprisesresurfacing the exposed surface to form a spherical surface portion usedas the bone interface surface.

Still further in accordance with the first embodiment, performing thedepth cut in some instances comprises forming the implant interfacesurface into a planar surface.

Still further in accordance with the first embodiment, harvesting thegraft in some instances comprises forming a cylindrical body between theimplant interface surface and the bone interface surface, an axis of thecylindrical body being normal to the implant interface surface.

Still further in accordance with the first embodiment, resurfacing theexposed surface in some instances comprises installing a first guide rodon the donor bone, and moving a resurfacing tool on the first guide rodto form said spherical surface portion.

Still further in accordance with the first embodiment, securing the cutguide instrument on the bone in some instances comprises sliding the cutguide instrument along the first guide rod and into abutment with theresurfaced exposed surface.

Still further in accordance with the first embodiment, harvesting thegraft in some instances comprises installing a second guide rod with asecond guide channel of the cut guide instrument on the donor bone andsliding an instrument on the second guide rod.

Still further in accordance with the first embodiment, harvesting thegraft in some instances comprises forming a peg bore in the graft, thepeg bore being coaxial with a hole in the donor bone made by insertionof the second guide rod.

Still further in accordance with the first embodiment, forming the pegbore in some instances is removing the second guide rod.

Still further in accordance with the first embodiment, a patientspecific alignment instrument in some instances has a receptaclereceiving and conforming to the bone interface surface and a hole in thereceptacle receiving and aligned with the peg bore to install theimplant onto the graft.

Still further in accordance with the first embodiment, the method insome instances further comprises sliding the patient specific alignmentinstrument along a guide pin to position and impact the implant andgraft on the recipient bone.

In accordance with a second embodiment of the present disclosure, thereis provided a system for generating a model of a patient specific cutguide instrument for harvesting a graft, comprising: a model of a graftdefined by an implant interface surface, a bone interface surface, and aspatial geometry therebetween, the model being specific to a patient; apatient-specific instrument generator for outputting the model of thepatient specific cut guide instrument, the patient-specific instrumentgenerator including a position determination module configured to orientand position at least a first guide axis, and to position an abutment ona model of a donor bone as a function of the spatial geometry, and aninstrument body generator module configured to generate a model of thepatient specific cut guide instrument comprising a body supporting a cutguide to perform a depth cut in the donor bone positioned and orientedas a function of a contact of the body with the abutment on the donorbone, and of the model of the graft, a first guide portion for alignmentwith the first guide axis, and at least one anchor guide for securingthe patient specific instrument cut guide on the donor bone as abuttedwith the abutment and aligned with the first guide axis, whereby thepatient specific cut guide instrument is configured to be used forharvesting the graft for subsequent implanting without alterations tothe spatial geometry of the graft.

Further in accordance with the second embodiment, the patient-specificinstrument generator in some instances further comprises a tool selectormodule for identifying at least one bone-altering tool to be used for atleast one of resurfacing the donor bone and harvesting the graft.

Still further in accordance with the second embodiment, the positiondetermination module in some instances is further configured todetermine a resurfacing of the donor bone to define the abutment, theresurfacing being to form a planar surface used as the implant interfacesurface.

Still further in accordance with the second embodiment, the instrumentbody generator module in some instances is further configured to orientthe cut guide in the body to form the bone interface surface intoanother planar surface, the exposed surface being non parallel to thebone interface surface.

Still further in accordance with the second embodiment, the toolselector module in some instances is further configured to identify abell saw to harvest the graft by forming a cylindrical body between theimplant interface surface and the bone interface surface, an axis of thecylindrical body being normal to the implant interface surface.

Still further in accordance with the second embodiment, the instrumentbody generator module in some instances is further configured togenerate the model of the patient specific cut guide instrument based onone of the Walch glenoid indication and Favard glenoid indication in areverse shoulder arthroplasty.

Still further in accordance with the second embodiment, a humerus insome instances is the donor bone, and the graft is configured to be usedto support an implant onto the glenoid in reverse shoulder arthroplasty.

Still further in accordance with the second embodiment, the guideportion in some instances is a guide channel sized to be used with aguide rod at the first guide axis.

Still further in accordance with the second embodiment, the toolselector module in some instances is further configured to select toolsthat are configured to slide along the guide rod and into contact withthe abutment.

Still further in accordance with the second embodiment, the instrumentbody generator module in some instances is further configured to definea hole in the body, the hole being sized as a function of a peg bore tobe formed in the graft, the peg bore being coaxial with a hole in thedonor bone made by insertion of the guide rod.

Still further in accordance with the second embodiment, the positiondetermination module in some instances is further configured todetermine a resurfacing of the donor bone to define the abutment, theresurfacing being to form a spherical surface portion used as the boneinterface surface.

Still further in accordance with the second embodiment, the instrumentbody generator module in some instances is further configured to orientthe cut guide in the body to form the implant interface surface into aplanar surface.

Still further in accordance with the second embodiment, the positiondetermination module in some instances is further configured to orientand position a second guide axis on the donor bone, the tool selectormodule identifies a bell saw to move along the second guide axis toharvest the graft by forming a cylindrical body between the implantinterface surface and the bone interface surface, an axis of thecylindrical body being normal to the implant interface surface.

Still further in accordance with the second embodiment, the instrumentbody generator module in some instances is further configured togenerate a model of a patient specific alignment instrument having areceptacle receiving and conforming to the bone interface surface and ahole in the receptacle receiving and aligned with a peg bore coincidentwith a hole along the second guide axis, to install the implant onto thegraft.

Still further in accordance with the second embodiment, the patientspecific alignment instrument in some instances further comprises aguide pin and channel assembly to position and impact the implant andgraft on the recipient bone.

Still further in accordance with the second embodiment, the toolselector module in some instances is further configured to select aresurfacing tool to move along a first guide rod coincident with thefirst guide axis on the donor bone for resurfacing the exposed surfaceinto said spherical surface portion.

Still further in accordance with the second embodiment, the patientspecific cut guide instrument for creating the graft in some instancescomprises a model file including a spatial model of a graft defined byan implant interface surface and a bone interface surface of the graftand a spacing therebetween; the body including a baseplate adapted to beabutted against the abutment, the cut guide adapted to receive therein acut blade, and at least one depth leg spacing the base plate away fromthe cut guide; wherein the base plate, the cut guide slot and the atleast one depth leg replicate parameters of the spatial model of thegraft.

The feature or features of one embodiment may be applied to otherembodiments, even though not described or illustrated, unless expresslyprohibited by this disclosure or the nature of the embodiments.

Some details associated with the present embodiments are described aboveand others are described below.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a humerus grafting patient-specificinstrument in accordance with a first embodiment of the presentdisclosure;

FIG. 2 is a schematic side view of the humerus grafting patient-specificinstrument of FIG. 1;

FIG. 3 is a transverse view showing a planned positioning of a glenoidimplant relative to a scapula;

FIG. 4 is the transverse view of FIG. 3, with a humerus graft positionedbetween the glenoid implant and the reamed glenoid;

FIG. 5 is a frontal view of a glenoid implant relative to a scapula inanother embodiment;

FIG. 6 is a frontal view of the glenoid implant and scapula of FIG. 5,with a humerus graft in the reamed glenoid;

FIG. 7 is a schematic view demonstrating a humerus with a guide rod;

FIG. 8 is a schematic view of the humerus of FIG. 7, with a reamer onthe guide rod;

FIG. 9 is a perspective view of the humerus of FIG. 8, with the humerusgrafting patient-specific instrument of FIG. 1 being slid on the guiderod;

FIG. 10 is a perspective view of the humerus of FIG. 9, with the humerusgrafting patient-specific instrument being pinned to the humerus;

FIG. 11 is a perspective view of the humerus of FIG. 10, with a cutblade guided by the humerus grafting patient-specific instrument of FIG.1;

FIG. 12 is a schematic side view of the humerus of FIG. 7, with a depthcut;

FIG. 13 is a schematic view of the humerus of FIG. 12, with a bell sawon the guide rod;

FIG. 14 is a schematic view of the humerus of FIG. 13, with lateralcuts;

FIG. 15 is a schematic view of the humerus of FIG. 14, with the glenoidimplant inserted into a graft for removal;

FIG. 16 is a schematic view of the humerus of FIG. 16 with the humerusgraft being harvested with the glenoid implant;

FIG. 17 is a perspective view of a humerus grafting patient specificinstrument in accordance with a second embodiment;

FIG. 18 is a side view of a glenoid implant relative to a glenoid cavityin accordance with the second embodiment;

FIG. 19 is a perspective view of the humerus with a hemisphericalreamer;

FIG. 20 is a perspective view of the humerus of FIG. 19, with thehumerus grafting patient-specific instrument of FIG. 17;

FIG. 21 is a perspective view of the humerus of FIG. 20, with a cutblade used with the humerus grafting patient-specific instrument of FIG.17;

FIG. 22 is a perspective view of the humerus of FIG. 21, with a guidepin being repositioned;

FIG. 23 is a perspective view of the humerus of FIG. 22, with a depthcut thereon;

FIG. 24 is a perspective view of the humerus of FIG. 23, with a sawbell;

FIG. 25 is a perspective view of a patient-specific barrel with aharvested humerus graft;

FIG. 26 is a perspective view of the patient-specific barrel withimpactor, glenoid implant and graft;

FIG. 27 is a side view of an impactor relative to the glenoid cavity inthe process of implanting the glenoid implant and graft;

FIG. 28 is a side view of a reamer reaming the glenoid cavity forreceiving the humerus graft harvested in FIGS. 17 to 24;

FIG. 29 is a side view of the humerus graft, glenoid implant in theresurfaced glenoid cavity; and

FIG. 30 is a block diagram of a system for generating a model of apatient specific cut guide instrument for harvesting a graft, inaccordance with the present disclosure.

DETAILED DESCRIPTION

Referring to the drawings, methods for harvesting a graft is generallyshown. The illustrated methods show the harvesting of a graft on thehumerus in a reverse shoulder arthroplasty, for example in an autograftor allograft situation (including a cadaver allograft). However, themethods may apply to other bones as well, for example using the iliaccrest as a donor bone. For simplicity, the examples of the presentdisclosure focus on a reverse shoulder arthroplasty with the humerus asdonor bone, although other bones could be used in accordance with thepresent disclosure.

In FIG. 1, a humerus grafting patient-specific instrument is generallyshown at 10. The humerus grafting patient-specific instrument 10 is saidto be patient-specific, in that its geometry is modeled based on aplanning for every patient's unique anatomy, using imaging techniques.Stated differently, the humerus grafting patient-specific instrument 10is developed subsequent to pre-operative steps by which a patient'sanatomy is modeled and the implant position is defined. Hence, thehumerus grafting patient-specific instrument 10 has an identity relatedto a patient, and is most likely inadequate for being used with otherpatients, whereby the instrument 10 is typically a one-time useinstrument. Accordingly, the humerus grafting patient-specificinstrument 10 has a model file 11 of non-transient format which featuresa two-dimensional or three-dimensional model of the patient's anatomyresulting from pre-operative imaging. The specific geometry of thecomponents of the humerus grafting patient-specific instrument 10 aredirectly related to the contents of the model file 11.

The humerus grafting patient-specific instruments of the presentdisclosure are designed to carve out a graft in the native humerus(e.g., especially in autograft procedure, but also in allograft), whichhumerus graft will be used as an interface between a glenoid cavity andan implant. The humerus is therefore in this example the donor bone,whereas the scapula is the receiver bone. Accordingly, the model file 11may define a specific spatial geometry for the humerus graft, featuringa glenoid interface surface that will lie against the reamed glenoid, animplant interface surface against which an undersurface of the implantwill lie, and lateral wall(s) between the glenoid interface surface andthe implant interface surface. The humerus grafting patient-specificinstruments and methods described herein are such that little or nomachining steps are required on the humeral graft once harvested.Indeed, some prior art techniques suggest removing a voluminous humeralgraft, to then suggest the machining of the graft prior to grafting. ThePSI technique taught herein allows the surgeon to plan the implantposition with a graft, while execution is intraoperative.

Referring to FIG. 1, the instrument 10 is shown as having a base plate12. The base plate 12 is shown as being generally circular (i.e.,disc-shaped) but other shapes are considered as well. A guide bore 13 isprovided through the base plate 12 and will be used as describedhereinafter as a guide for translational/rotational movements. One ormore depths legs 14 project from the base plate 12 and support a cutslot 15—with pin guides 15A—at ends opposite to the base plate 12. Thecut slot 15 is configured to receive a cut blade therein. As shown inFIG. 2, the length of the depth legs 14 is illustrated as H1 and H2(determined using the surgeon planning of the implant relative to theglenoid). With reference to FIG. 3, it is shown that H1 and H2 may berepresentative of two distinct dimensions between a glenoid implant 20and a glenoid cavity C, the glenoid implant 20 shown as having a baseplate 21 and a peg 22. The base plate 21 is optional in the implant 20,and supports a tapered head 23 that will be part of the shoulder joint.The H1 and H2 dimensions are based on a planning indication known asWalch glenoid indication, in which the glenoid cavity is reamed into aplane without sacrificing excessively the glenoid cavity surface. H1 andH2 are representative of the spacing between the base plate 21 and thereamed glenoid cavity C (i.e., the recipient site or location) as shownin FIG. 4, whereby the harvesting of graft should have dimensions H1 andH2 to replicate the assembly shown in FIG. 4. The positioning of theglenoid implant 20 also takes into consideration a depth of insertion ofthe peg 22 in the shoulder blade S. Accordingly, the humerus graftingpatient-specific instrument 10 is devised so as to harvest humerus graftG of FIG. 4.

Alternatively, the assessment of H1 and H2 may be based on a Favardglenoid indication as shown in FIGS. 5 and 6. Whether the glenoidimplanting is based on the Walch glenoid indication, the Favard glenoidindication or other implanting in which the glenoid surface is planar,the instrument 10 will be similar with, however, an adjustment of thelength of the depth legs 14 as per dimensions H1 and H2, dependent onwhich of the indications will be used in the planning stages of surgery.

With the instrument 10 being created in pre-operative planning, a methodfor harvesting the humerus graft G may be performed using the instrument10, as described hereinafter.

In FIG. 7, a guide rod 30 is positioned in the humerus H in preparingfor the humerus grafting. Although not shown, the positioning of theguide rod 30 may result from the use of different pins and drills toproperly orient the guide rod 30, to a desired depth. Otherpatient-specific instruments may be used to properly orient the guiderod 30, or other technologies such as inertial sensors.

Referring to FIG. 8, the guide rod 30 is used with a flat reamer 40. Theflat reamer 40 is of the type having a hollow cylinder 41 at the end ofwhich is a disc 42. Accordingly, by use of the reamer 40, the humerus Hmay have its head flattened as shown in FIG. 9. The flattened head couldform the implant interface surface of the graft G. It is also consideredto use the native surface without machining same, for example if it hasa desired shape (e.g., substantially planar), or if the implantinterface surface of the implant may be patient specifically shaped forcomplementary “negative” engagement with the native surface.

Once the head is flattened as in FIG. 9, the humerus graftingpatient-specific instrument 10 may be slid onto the humerus H, using theguide rod 30 to form a joint with the base plate 12 of the instrument10. The diameter of the guide bore 13 of the base plate 12 of theinstrument 10 is sized so as to precisely fit onto the guide rod 30.Once the base plate 12 lays flat against the flattened surface of thehumerus H (constituting the abutment), as shown in FIG. 10, the cut slot15 may be pinned to the humerus H by way of pin(s) 50. It is pointed outthat, in the illustrated embodiment, the orientation of the instrument10 relative to the humerus H is of lesser importance than therequirement for the base plate 12 to be flat and in abutment against thehumerus H.

Referring to FIG. 11, with the instrument 10 pinned to the humerus H bythe pins 50, cut blade 60 may be used in the cut slot 15 to perform adepth cut D, to define the glenoid interface surface of the graft G. Itmay be required to remove the guide rod 30 prior to performing the depthcut with the cut blade 60 so as not to have the guide rod 30 interferewith the cut blade 60. This is dependent on the depth of the guide rod30. In such a case, the pins 50 ensure that the instrument 10 remainsanchored to the humerus H during the depth cut.

As shown in FIG. 12, once the depth cut D is made, the guide rod 30 maybe reinserted into the humerus H, for a bell saw 70, also known as acylindrical reamer, to be used to perform the lateral cut, as shown inFIG. 14. This results in the detachment of the humerus graft G from aremainder of the humerus H. The bell saw 70 may have a depth scalethereon, to provide a visual display of depth.

In FIG. 15, there is illustrated a technique for removing the humerusgraft G, using the glenoid implant 20. By this method, the glenoidimplant 20 is forced into the humerus graft G, requiring for example themachining of a bore of adequate dimension in the humerus graft G, untilthe base plate 21 of the glenoid implant 20 is flush against the surfaceof the humerus graft G. The humerus graft G is harvested as shown inFIG. 16 by pulling out the glenoid implant 20. At that point, it ispossible to install the assembly of humerus graft G and glenoid implant20 in the manner shown in FIGS. 4 and 6, and this may require somereaming and peg drilling to the glenoid cavity C. Fasteners of anyappropriate type, and tools (e.g., impactor) may be used to properlyimplant the combination of the humerus graft G and glenoid implant 20.Also, cement or like adhesive can be used to fasten the graft to theimplant.

The embodiment described above for the instrument 10 is commonly usedwhen glenoid deformities are generally planar, or machined to be planaras planned. This is a common occurrence and is advantageous as flatreaming minimizes subchondral bone sacrifice. The geometry of the graftG may be defined as having a cylindrical body. A peg bore may be definedalong the central axis of the cylindrical body, for the implant peg topass through the cylindrical body. The central axis of the cylindricalbody may be normal to the first end surface of the cylindrical body,whereas the second end surface of the cylindrical body is oblique. Inother words, a plane in which lies the second end surface is notparallel to a plane in which lies the first end surface. The anglebetween the planes is less than 90 degrees, and is commonly between 5and 45 degrees, although it could be out of that range. Therefore, allthree surfaces of the graft G may be machined, in three different steps,while being on the native bone. The machining of the peg bore may be ina fourth separate step, or may consist in the removal of the guide pin30, the guide pin 30 being selected to have a diameter matching that ofthe peg 22. Although described as being donated by the humerus, thegraft G may be harvested from other sites, such as the iliac crest.

Now that the humerus grafting patient specific instrument 10 has beendescribed as used for a flat glenoid surface, another embodiment of ahumerus grafting patient specific instrument is set forth, for afrusto-spherical glenoid cavity, i.e., the glenoid cavity is a spheresegment surface. Indeed, in some instances, the erosion is sphericalwith a glenoid surface medialization due to wear. This is for instanceshown in FIG. 18.

Therefore, referring to FIG. 17, there is illustrated a humerus graftingpatient specific instrument 100 to be used for hemispherical orfrusto-spherical glenoid cavities. In similar fashion to the instrument10, the instrument 100 is patient specific and has a model file 101featuring modelisation of the patient's anatomy obtainedpre-operatively. The instrument 100 has a first guide 102 and a secondguide 103, both generally elongated cylindrical portions with channelsof circular section that would be mounted onto pins and thus formsliding joints. A depth leg 104 projects from the first guide 102 andhas a cut slot 105 (with pin guides 105A) at an end thereof.

Referring to FIG. 18, a schematic planning view is provided showing thedesired positioning of the glenoid implant 20 relative to the glenoidcavity C. As observed, the glenoid cavity C has a circular outline(circle O shown in FIG. 18), indicative of a frusto-spherical cavity,with a distance D between an underface of the baseplate 21 of theglenoid implant 20 and a bottom of the glenoid cavity C. The depth D isrepresentative of the height of the humerus graft G to be harvested fromthe humerus H. Moreover, angle α is also to be taken into consideration,as the angle between the axis of the peg 22 of baseplate 21 and line L.Line L passes through point P at the intersection of the axis of the peg22 with the circle O, and through the center of the circle. All theseparameters are obtained preoperatively from the surgeon planning of theimplanting procedure relative to the glenoid surface and are part of themodel file 101. These parameters are descriptive of the spatial geometryof the graft G to interface the implant 20 to the reamed glenoid cavityC.

Referring to FIG. 19, in order to start the grafting procedure, ahemispherical reamer 110 is used to surface the humerus head H into afrusto-spherical shape. Hemispherical reamer 110 has a hollow cylinder111 that is cannulated to be mounted on the guide rod 30. A saw edge 112is sized as a function of the dimension of the diameter of the circle Oof FIG. 18. Accordingly, various sizes of the hemispherical reamer 110may be provided, with the operator selecting the appropriate size basedon the pre-operative planning and on the model file 101. Hence, thereamed humerus head H has the glenoid interface surface machined ontoit.

Once the humerus head has been shaped, the instrument 100 may bepositioned thereon using the guide rod 30. The guide rod 30 serves as ashaft for the second guide 103, with the angle between the first guide102 and the second guide 103 being angle α.

Referring to FIG. 21, once the instrument 100 abuts against the humerusH, it may be pinned using pin(s) 50. The guide rod 30 may be removed forthe cut blade 60 to perform a depth cut of depth D, to form the implantinterface surface of the graft G. Once the depth cut has been made, theguide 130 may be repositioned onto the humerus H, but this time usingthe first guide 102, as shown in FIG. 22.

Referring to FIG. 23, a drill tool 120 may then be used to machine abore in the humerus H, which bore is sized based on the diameter of thepeg 22 of the implant 20, as it will receive the peg 22 therein.

Referring to FIG. 24, the saw bell 70 may then be used in order todefine the size of the graft G to be harvested. Accordingly, based onthe preceding steps, humerus graft G is shaped for use in theconfiguration of FIG. 18, and may be harvested.

In order to implant it properly (or implant the graft G harvested usingthe instrument 10) and replicate the planning by setting the graft axialrotation appropriately, different tools may be devised, such as barrel130 of FIG. 25. The barrel 130 has a cavity 131 that is shaped inpatient specific manner, in similar fashion to the instruments 10 and100. As such, barrel 130 may have a model file. A peg bore 132 is abottom of the cavity 131, and sized and positioned specifically based onthe planned interrelation between the peg 22 and the graft G.Accordingly, the alignments of the peg bore 132, the barrel 130 and thepeg bore in the humerus graft G ensure that a single orientation of thehumerus graft G in the barrel 130 is achieved, for insertion of the peg22 in the manner shown in FIG. 26. The barrel 130 further comprises aguide 133 that cooperates with a pin 134 to form a sliding joint.

As shown in FIG. 26, an impactor 140 has an implant end 141 devised tosupport the tapered head 23 of the implant 20. The impactor 140 also hasat an opposite end an impact end 142 adapted to be impacted forimplanting the implant 20. The impactor 140 also has a guide 143 thatwill collaborate with the pin 134. This is shown particularly in FIG. 27in which it is observed that the impactor 140 is guided by the implantedpin 134 to perform the impacting action. The graft could be cemented tothe baseplate and not impacted.

Referring to FIG. 28, it may however be necessary to machine the glenoidcavities C using a reamer 150 having an arcuate cutting tool 151. It ispointed out that the barrel 130 may be used to machine the glenoidcavities so as to define the peg bore into the glenoid. Accordingly, theimplant 20 and the harvested graft G may be implanted in the reamedglenoid cavity C in the manner shown in FIG. 29.

The geometry of the graft G may be defined as having a cylindrical body,although an axial length of the cylindrical body may be close to zero ata location. A peg bore may be defined along the central axis of thecylindrical body, for the implant peg to pass through the cylindricalbody. The central axis of the cylindrical body may be normal to thefirst end surface of the cylindrical body, whereas the second endsurface of the cylindrical body is spherical. The center of thespherical surface is not aligned with the central axis of thecylindrical body, i.e., it is not coincident with the central axis.Therefore, all three surfaces of the graft G may be machined, in threedifferent steps, while being on the native bone. The machining of thepeg bore may be in a fourth separate step. The machining of the peg boremay be in a fourth separate step, or may consist in the removal of theguide pin 134, the guide pin 134 being selected to have a diametermatching that of the peg 22. Although described as being donated by thehumerus, the graft G may be harvested from other sites, such as theiliac crest.

Therefore, the method can generally be described as a method forcreating a graft. According to the method, a cut guide instrument 10 or100 is obtained, and is specific to a patient's anatomy. The instrument10 or 100 is the result of pre-operative planning in which the patient'sanatomy is modeled, and the spatial geometry of a graft is defined fromthe surgeon planning by the planning software. Intraoperatively, anexposed surface of a donor bone is resurfaced, to form an implantinterface surface (in the case of instrument 10) or a bone interfacesurface (in the case of instrument 100) of the graft G. The cut guideinstrument 10 or 100 is then secured to the donor bone. Using the cutguide instrument 10 or 100, a depth cut in performed the donor bone toform the other of the implant interface surface or the bone interfacesurface of the graft G. It may be required to further machine the graftG, or the graft G may be harvested right away, for example if theresurfacing has also been used to define the lateral surfaces of thegraft G.

While the method described above provides an example of shouldersurface, the method could also be used with other joints, or for anon-reverse shoulder surgery.

Referring to FIG. 30, there is illustrated a system 200 for generating amodel of a patient specific cut guide instrument, such as 10, 100, forharvesting a graft, such as G, for subsequent fabrication and used basedon the methods illustrated in FIGS. 1-29. In order to generate the modelof the patient specific cut guide instrument, such for example at 11,101 in FIGS. 1, 17 and 30, the system 200 must have a model 201 of thegraft G. The model 201 is for example the result of pre-operativeplanning, in which a virtual positioning and orienting of an implant isdone on images of a bone. This may be illustrated for example by FIGS.3, 4 and 18, with the graft G being defined by an implant interfacesurface, a bone interface surface, and a spatial geometry therebetween.The model is specific to a patient, in that it results from an analysisof the patient's data (imagery of bone, for example in 3D, patientcondition, etc). The system 200 may also have a model 202 of the donorbone, such as the humerus H. The graft G will be harvested in the donorbone, and therefore the system 200 determines how to alter the donorbone to harvest the graft G, using the model 202. As describedpreviously, the patient specific cut guide instrument 10 is used forharvesting the graft for subsequent implanting without alterations tothe outer surface of the graft G, i.e., after harvesting, the graft Galready has a geometry corresponding to the model of the graft 201. Sometrivial machining may occur after harvesting, such as machining a peghole of appropriate dimension in the hole remaining from the pin guide30. However, such machining is not to alter the outer surface of thegraft B, i.e., the cylindrical body and its ends.

A patient-specific instrument generator 203 outputs the model 11, 101 ofthe patient specific cut guide instrument 10, 100. The patient-specificinstrument generator 203 has a processor unit for operating modules thatgenerate data resulting in the model 11, 101, using models 201 and 202.The patient-specific instrument generator 203 may have a positiondetermination module 204 for orienting and positioning a guide axis oraxes, taking into consideration the spatial geometry of the graft G, viathe model 201, to make sure there is sufficient bone available for thegraft G, without damaging what must remain of the donor bone, as permodel 202. As observed in FIGS. 1-29, the axes are used to correctlyposition and orient the instrument 10, 100 on the donor bone, and toguide the tools altering the bone. The position determination module 204may also position an abutment on the model 202 of a donor bone as afunction of the spatial geometry. This may include identifying that thedonor bone must be resurfaced to define the abutment, as in FIGS. 8 and19.

Once the position determination module 204 has produced the orientationand position of the axis, and determined the abutment (includingresurfacing), an instrument body generator module 205 generates themodel 11, 101 of the patient specific cut guide instrument 10, 100. Asobserved in FIGS. 1-29, the instrument 10,100 has a body supporting acut guide with the cut slot 15. The cut guide is used with a cuttingtool, such as a saw, to perform a depth cut in the donor bone, the depthcut being positioned and oriented as a function of the contact of thebody with the abutment on the donor bone, of the model 201 of the graft,and of the guide axis (axes). One or more guide channels are part of thebody for alignment with the guide axis (axes). One or more anchorguides, such as the pin guides 15A, are located in the body of theinstrument 10, 100 for securing the patient specific instrument cutguide 10, 100 on the donor bone as abutted with the abutment and alignedwith the guide axis. The instrument body generator module 205 may alsocreate other patient specific instruments, such as the barrel 130. Thegenerator 205 outputs a model(s) 11, 101, in any appropriate format,such as non-transient instructions to machine the instrument 10, 100, a3D printing file, etc.

In the system 200, the patient-specific instrument generator 203 mayalso have a tool selector module 206. The module 206 may identify thevarious bone-altering tools, such as 30, 40, 70, 120, etc (concurrentlyas 210) to be used for resurfacing the donor bone, harvesting the graft,etc. The module 206 may also provide data such as depth of penetrationin the case of the bell saw 70.

1. A method for harvesting a graft having at least an implant interfacesurface, a bone interface surface, and a planned spatial geometrytherebetween, the method comprising: obtaining a cut guide instrumentspecific to a patient's anatomy; resurfacing an exposed surface of adonor bone to form one of an implant interface surface and a boneinterface surface of the graft; securing the cut guide instrument to thebone relative to resurfaced exposed surface; performing a depth cut inthe donor bone to form the other of the implant interface surface andthe bone interface surface of the graft with the planned spatialgeometry; and harvesting the graft from the donor bone.
 2. The methodaccording to claim 1, wherein resurfacing the exposed surface of thedonor bone comprises resurfacing the exposed surface to form a planarsurface used as the implant interface surface.
 3. The method accordingto claim 2, wherein performing the depth cut comprises forming the boneinterface surface into another planar surface, the exposed surface beingnon parallel to the bone interface surface.
 4. The method according toclaim 3, wherein harvesting the graft comprises forming a cylindricalbody between the implant interface surface and the bone interfacesurface, an axis of the cylindrical body being normal to the implantinterface surface.
 5. The method according to claim 2, whereinharvesting the bone comprises securing an implant against the implantinterface surface and removing the implant and graft from the donorbone.
 6. The method according to claim 1, wherein harvesting the graftcomprises harvesting the graft to obtain the spatial geometry based onone of the Walch glenoid indication and Favard glenoid indication in areverse shoulder arthroplasty.
 7. The method according to claim 1,wherein harvesting the graft comprises harvesting the graft from ahumerus being the donor bone, and further comprising implanting thegraft and an implant onto the glenoid in reverse shoulder arthroplasty.8. The method according to claim 1, further comprising implanting thegraft onto a recipient bone without further alterations to the graftafter said harvesting from the donor bone.
 9. The method according toclaim 1, wherein resurfacing the exposed surface comprises installing aguide rod and moving a resurfacing tool on the guide rod.
 10. The methodaccording to claim 9, wherein securing the cut guide instrument on thebone comprises sliding the cut guide instrument along the guide rod andinto abutment with the exposed surface.
 11. The method according toclaim 9, further comprising forming a peg bore in the graft, the pegbore being coaxial with a hole in the donor bone made by insertion ofthe guide rod.
 12. The method according to claim 11, wherein forming thepeg bore is removing the guide rod.
 13. The method according to claim 1,wherein resurfacing the exposed surface of the donor bone comprisesresurfacing the exposed surface to form a spherical surface portion usedas the bone interface surface.
 14. The method according to claim 13,wherein performing the depth cut comprises forming the implant interfacesurface into a planar surface.
 15. The method according to claim 14,wherein harvesting the graft comprises forming a cylindrical bodybetween the implant interface surface and the bone interface surface, anaxis of the cylindrical body being normal to the implant interfacesurface.
 16. The method according to claim 13, wherein resurfacing theexposed surface comprises installing a first guide rod on the donorbone, and moving a resurfacing tool on the first guide rod to form saidspherical surface portion.
 17. The method according to claim 16, whereinsecuring the cut guide instrument on the bone comprises sliding the cutguide instrument along the first guide rod and into abutment with theresurfaced exposed surface.
 18. The method according to claim 15,wherein harvesting the graft comprises installing a second guide rodwith a second guide channel of the cut guide instrument on the donorbone and sliding an instrument on the second guide rod.
 19. The methodaccording to claim 18, wherein harvesting the graft comprises forming apeg bore in the graft, the peg bore being coaxial with a hole in thedonor bone made by insertion of the second guide rod.
 20. The methodaccording to claim 19, wherein forming the peg bore is removing thesecond guide rod.
 21. The method according to claim 19, furthercomprising using a patient specific alignment instrument having areceptacle receiving and conforming to the bone interface surface and ahole in the receptacle receiving and aligned with the peg bore toinstall the implant onto the graft.
 22. The method according to claim21, wherein using the patient specific alignment instrument furthercomprises sliding the patient specific alignment instrument along aguide pin to position and impact the implant and graft on the recipientbone.
 23. The method according to claim 1, wherein harvesting the graftcomprises harvesting a cadaver allograft. 24-40. (canceled)